Zobrazeno 1 - 10
of 163
pro vyhledávání: '"Alok C Gupta"'
Autor:
Mauri J. Valtonen, Staszek Zola, Alok C. Gupta, Shubham Kishore, Achamveedu Gopakumar, Svetlana G. Jorstad, Paul J. Wiita, Minfeng Gu, Kari Nilsson, Alan P. Marscher, Zhongli Zhang, Rene Hudec, Katsura Matsumoto, Marek Drozdz, Waldemar Ogloza, Andrei V. Berdyugin, Daniel E. Reichart, Markus Mugrauer, Lankeswar Dey, Tapio Pursimo, Harry J. Lehto, Stefano Ciprini, T. Nakaoka, M. Uemura, Ryo Imazawa, Michal Zejmo, Vladimir V. Kouprianov, James W. Davidson Jr., Alberto Sadun, Jan Štrobl, Z. R. Weaver, Martin Jelínek
Publikováno v:
The Astrophysical Journal Letters, Vol 968, Iss 2, p L17 (2024)
We report the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ 287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifre
Externí odkaz:
https://doaj.org/article/e6e575b905e5482a8bee0479a0634bbd
Autor:
Wenwen Zuo, Hengxiao Guo, Jingbo Sun, Qi Yuan, Paulina Lira, Minfeng Gu, Philip G. Edwards, Alok C. Gupta, Shubham Kishore, Jamie Stevens, Tao An, Zhen-Yi Cai, Hai-Cheng Feng, Luis C. Ho, Dragana Ilić, Andjelka B. Kovačević, Sha-Sha Li, Mar Mezcua, Luka Č. Popović, Mouyuan Sun, Tushar Tripathi, Vivian U, Oliver Vince, Jianguo Wang, Junxian Wang, Shu Wang, Xuebing Wu, Zhenya Zheng
Publikováno v:
The Astrophysical Journal, Vol 974, Iss 2, p 288 (2024)
To investigate the short-term variability and determine the size of the optical continuum emitting region of intermediate-mass black holes (IMBHs), we carried out high-cadence, multiband photometric monitoring of a Seyfert 1 galaxy J0249−0815 acros
Externí odkaz:
https://doaj.org/article/84f6e6d430d04084b24523678c74067a
Autor:
Alok C. Gupta, Pankaj Kushwaha, Mauri J. Valtonen, Sergey S. Savchenko, Svetlana G. Jorstad, Ryo Imazawa, Paul J. Wiita, Minfeng Gu, Alan P. Marscher, Zhongli Zhang, Rumen Bachev, G. A. Borman, Haritma Gaur, T. S. Grishina, V. A. Hagen-Thorn, E. N. Kopatskaya, V. M. Larionov, E. G. Larionova, L. V. Larionova, D. A. Morozova, T. Nakaoka, A. Strigachev, Yulia V. Troitskaya, I. S. Troitsky, M. Uemura, A. A. Vasilyev, Z. R. Weaver, A. V. Zhovtan
Publikováno v:
The Astrophysical Journal Letters, Vol 957, Iss 1, p L11 (2023)
We study the optical flux and polarization variability of the binary black hole blazar OJ 287 using quasi-simultaneous observations from 2015 to 2023 carried out using telescopes in the USA, Japan, Russia, Crimea, and Bulgaria. This is one of the mos
Externí odkaz:
https://doaj.org/article/4386a01033bb441a9e21f8c1d6df1ce8
Autor:
Mauri J. Valtonen, Lankeswar Dey, Achamveedu Gopakumar, Staszek Zola, Anne Lähteenmäki, Merja Tornikoski, Alok C. Gupta, Tapio Pursimo, Emil Knudstrup, Jose L. Gomez, Rene Hudec, Martin Jelínek, Jan Štrobl, Andrei V. Berdyugin, Stefano Ciprini, Daniel E. Reichart, Vladimir V. Kouprianov, Katsura Matsumoto, Marek Drozdz, Markus Mugrauer, Alberto Sadun, Michal Zejmo, Aimo Sillanpää, Harry J. Lehto, Kari Nilsson, Ryo Imazawa, Makoto Uemura
Publikováno v:
Galaxies, Vol 11, Iss 4, p 82 (2023)
We present a summary of the results of the OJ 287 observational campaign, which was carried out during the 2021/2022 observational season. This season is special in the binary model because the major axis of the precessing binary happens to lie almos
Externí odkaz:
https://doaj.org/article/f417436aeaf440128c5aa7366d0a29a7
Autor:
Beatriz Villarroel, Geoffrey W. Marcy, Stefan Geier, Alina Streblyanska, Enrique Solano, Vitaly N. Andruk, Matthew E. Shultz, Alok C. Gupta, Lars Mattsson
Publikováno v:
Scientific Reports, Vol 11, Iss 1, Pp 1-8 (2021)
Abstract Nine point sources appeared within half an hour on a region within $$\sim $$ ∼ 10 arcmin of a red-sensitive photographic plate taken in April 1950 as part of the historic Palomar Sky Survey. All nine sources are absent on both previous and
Externí odkaz:
https://doaj.org/article/3e494acb37db4e5fa5fca631ce66b700
Publikováno v:
The Astrophysical Journal, Vol 960, Iss 1, p 11 (2023)
We have analyzed the optical light curves of the blazar OJ 287 obtained with the Transiting Exoplanet Survey Satellite over about 80 days from 2021 October 13 to December 31, with an unprecedented sampling of 2 minutes. Although significant variabili
Externí odkaz:
https://doaj.org/article/e4d255b2ab8640d889fd3c18b72caee3
Publikováno v:
The Astrophysical Journal, Vol 950, Iss 2, p 173 (2023)
The continuous monitoring capability of Fermi-LAT has enabled the exploration of quasiperiodic oscillations (QPOs) in the γ -ray light curve of blazars that has given a new perspective to probe these sources over a wide range of timescales. We repor
Externí odkaz:
https://doaj.org/article/db1657f098224cf88a16a5a80ed1f5f4
Autor:
Q. Yuan, Pankaj Kushwaha, Alok C. Gupta, Ashutosh Tripathi, Paul J. Wiita, M. Zhang, X. Liu, Anne Lähteenmäki, Merja Tornikoski, Joni Tammi, Venkatessh Ramakrishnan, L. Cui, X. Wang, M. F. Gu, Cosimo Bambi, A. E. Volvach
Publikováno v:
The Astrophysical Journal, Vol 953, Iss 1, p 47 (2023)
We perform correlation and periodicity search analyses on long-term multiband light curves of the flat-spectrum radio quasar PKS 1510−089 observed by the space-based Fermi-Large Area Telescope in γ -rays, the SMARTS and Steward Observatory telesco
Externí odkaz:
https://doaj.org/article/6ec1d940f76b469ebc9c7ef4a6c99f70
Publikováno v:
The Astrophysical Journal, Vol 943, Iss 1, p 53 (2023)
We report the detection of several quasiperiodicities around 0.6–2.5 days in the optical emission of the blazar S4 0954+658. The source was observed by the Transiting Exoplanet Survey Satellite in six sectors and it showed these features in all but
Externí odkaz:
https://doaj.org/article/c543fa2c441042b98d85358d0b92d29c
Autor:
Nibedita Kalita, Yuhai Yuan, Minfeng Gu, Junhui Fan, Yosuke Mizuno, Peng Jiang, Alok C. Gupta, Hongyan Zhou, Xiang Pan, Anton A. Strigachev, Rumen S. Bachev, Lang Cui
Publikováno v:
The Astrophysical Journal, Vol 943, Iss 2, p 135 (2023)
BL Lacertae underwent a series of historical high flux activity over a year from 2020 August in the optical to VHE γ -rays. In this paper, we report on optical flux and spectral variability of the first historical maxima outburst event during Octobe
Externí odkaz:
https://doaj.org/article/46a3e90b89854ad79df0b8c0399682e7